It has been known for a long time that many plant materials contain phenols or phenolic compounds. The term phenols, phenolic compounds or plant phenolics in the context of plant materials and in the context of the present application for patent refer to a multitude of naturally occurring substances which have one or more phenolic hydroxyl groups. As is known, a phenolic hydroxyl group is a hydroxyl group (OH) attached to a carbocyclic aromatic ring. Phenol (hydroxybenzene) is the simplest example of a phenolic compound, but the naturally occurring phenols or phenolic compounds tend to be of more complex structure, and include polyphenols having complex substitution patterns and compounds having condensed rings. Phenolics isolated from plants including seeds and fruits of plants include gallic acid, flavan-3-ols, flavonols, phloridzin, cinnamates, hydroxymethyl furfural and anthocyanins.
Phenolics compounds contained in plant materials, particularly in plant materials from which proteins are isolated for human or animal consumption, have long been considered undesirable. This is primarily because phenolics tend to bind strongly to proteins (by hydrogen bonds) and also by covalent bonds, and tend to provide undesired color to the plant protein isolates. Whereas the present applicant does not wish to be bound by theory, it is noted that the process by which phenolic compounds are bound to proteins is generally understood to involve a step of oxidation that occurs while the plant isolate is in aqueous suspension or solution, and is exposed to atmospheric oxygen, or to oxygen dissolved in water, followed by a 1,4 addition (Michael addition) of a sulfhydryl (SH) or amino (NH) function of the protein to the resulting quinone. This series of reactions is illustrated below in a simplified form. The reaction below is simplified, because the plant phenolic compound is not simple phenol or hydroquinonone as illustrated below, but a more complex phenolic compound of the nature described above. The group R in the simplified scheme represents the rest of the plant protein molecule, just like the simple phenol or hydroquinone in the simplified scheme represents the more complex phenolic compound naturally occurring in the plant.

A detailed description and review of the chemistry of the attachment of plant phenolics to plant proteins by hydrogen bonding and through oxidation to quinones followed by 1,4 (Michael) addition, can be found in the publication by Loomis et al., “Plant phenolic compounds and the isolation of plant enzymes” Phytochemistiy, 5,423, (1966).
Because the plant phenolics are generally considered in the prior art to be undesirable contaminants of proteins which are isolated from the plant, the prior art has strived to isolate the proteins flee of the phenolics, and to discard the undesirable phenolics while keeping the desired protein material. Thus, processes for removing the phenolics from plant proteins, and to isolate proteins as free of phenolic contaminants as possible, are described in several publications and patents, such as:
Lusas “Sunflower Seed Protein”, New Protein Foods, 5, 393-433, (1985);
Sodini et al. J. Agric. Food Chem., 25, 822-825, (1977), and
Pearce U.S. Pat. No. 4,435,319.
Perhaps because of the difficulty or expense of removing “undesirable” phenolics from phenolics-rich plant flours, the phenol-rich flours are typically considered to be of poor quality for human or animal consumption and are hence abundant and inexpensive. These typically are by-products of oil extraction (e.g., flax meal) or represent a by-product of a specialized milling fraction (e.g., buckwheat).
In addition to being considered undesirable as a colorant, plant phenolics were also suggested to have anti-nutritive value (Food Phenolics, Chapter 6, p. 171-9, 1995).
On the other hand, it has been relatively recently recognized in the prior art that oral consumption of antioxidants increases serum antioxidant levels (see Rao et al., J. Medicinal Food, Mar. 15, 2000) and that orally consumed anti-oxidants have beneficial value to human (and other mammalian) health. More specifically, the health benefits or potential benefits shown by epidemiological studies and generally attributed to consumption of anti-oxidant rich food or food supplements include or relate to prevention of various cancers, decrease in the incidence of cardiovascular disease, and decrease in the incidence of stroke. Recognizing the importance of anti-oxidants in foods or food supplements, the prior art has actually developed an assay for determining the amount of anti-oxidants contained in a food product. The assay termed the Oxygen Radical Absorbance Capacity Assay (ORAC) is described by Cao et al., in Clinical Chemistry, 41, 1738, 1995. This assay allows one to quickly compare the total antioxidant capacity of various food servings (Prior et al. J. Amer. Nutraceutical Assoc., 2, 46, (1999)).
As an exception to the prior art generally making great efforts to remove undesirable phenolics from isolated plant proteins, buckwheat protein from which phenolics have not been removed has been reportedly fed to experimental rats, as is described in a series of publications:
Kayashita et al., Nutrition Research, 15, 691-8, 1995;
Kayashita et al., J. Nutrition 127, 1395, 1997;
Kayashita el al., Biosci. Biotechnol. Biochem., 60, 1530, 1996;
Kayashita et al., Current Advances in Buckwheat Research, 935, 1995;
Kayashita et al., BioSci. Biotechnol. Biochem., 63, 1242, 1999, and
Kayashita et al., BioSci. Biotechnol. Biochem., 63, 1837, 1999.
In these publications about buckwheat protein, the authors suggest that whatever health effects were observed in the experimental rats they were entirely due to the protein composition of the buckwheat versus soy protein or casein. The authors discuss in detail the amino acid profiles of buckwheat protein and find several features of buckwheat protein that suggest health benefits. Indeed, buckwheat has been shown in the prior art to have great health benefits independent of its protein or phenol content. Hence, any phenolic compounds which may have been present in the buckwheat protein of these experiments would have been considered impurities, and thus feeding of protein-phenol complexes to animals is not suggested by these publications of Kayashita et al.